Mobile computing devices, such as smartphones, are becoming ever more powerful, both in terms of processing power and in terms of capabilities. Such expanded capabilities include capabilities to determine the geographic location of a device. For example, global positioning system (GPS) receivers on mobile devices can provide very fine positioning capabilities and are becoming very common on mobile devices. Other approaches, such as finding or at least estimating a location of a device using WiFi access points and Cell ID's can also be used. Such features may be particularly useful for various on-line location-based services that provide rich applications that, for proper functioning, need to be able to determine a user's location automatically. One such type of location-based service includes applications for identifying the current up-to-date locations of a user's friends or acquaintances. Such services can generate a map that is overlaid with an icon of each one of a user's friends. The services can help the friends determine that they should meet for food, drink, or just conversation, if they are proximate to each other.
Location-based services (LBS) can be expensive, however, in turns of electrical power consumption. The use of regular GPS readings to constantly pinpoint a user's location can cut a smartphone's battery time in half or more. Readings from WiFi access points generally require less power, but enough that repeated readings will also substantially decrease observed battery life for a user of such devices.